When you develop trust, you can more easily accomplish what they say is the ideal outcome in almost any scenario: win-win. So don't use deception for short-term gain, because, they write: "It does not build long-term relationships or encourage your counterpart to come back and negotiate with you again at a later date."

Deepak Malhotra: a Harvard Business School professor and expert on the art of negotiation.

Adam Jeffery | CNBC

That's why they recommend being mindful of your nonverbal cues, too. Opening your palms, for instance, gives off the impression that you are an honest person. "It goes back to medieval days when open palms indicated that a person had no weapons," they write. "Today they generally indicate that a person has nothing to hide."

More importantly, they stop liking you. "Don't underestimate the importance of likability," says Harvard Business School's Deepak Malhotra. "It's crucial: People are going to fight for you only if they like you."

He adds: "Anything you do in a negotiation that makes you less likable reduces the chances that the other side will work to get you a better offer."